Moondrop. Because this fidget toy's calibrated design of metal and magnets makes it feel like you're dropping the aluminum slider down its shaft from the moon, at a precise gravity of 1.6 m/s squared. Or, you could choose a copper slider over the aluminum one, and drop from 3.7 m/s-squared Mars. Or, by removing the magnets from the Moondrop shaft, plain old 9.8 m/s-squared Earth. Think of it this way: Moondrop Lunar is a really, really, really slow handjob. Moondrop Mars is a really, really slow handjob. And Moondrop Earth is a slow handjob (well, maybe it's normal speed for some, buy my hand usually works well beyond the force of gravity.)
Don't want to think about handjobs right now? Check out this GIF of the Moondrops side-by-side instead. Then check out this GIF of all the cool, fidgety things you can do with a--or two or three--of your own Moondrops.
Moondrop Lundar has an all-aerospace-grade-aluminum construction, with the slider falling 38mm in exactly 0.22 seconds, the same time it would take any object to fall that distance on the moon. Moondrop Mars adds a heavier copper slider to overcome the magnets inside the toy's shaft a little faster; it falls from top to bottom in 0.13 seconds, just as the smartphone I butter finger daily would on Mars. You can make a Moondrop Earth from either the Lunar or the Mars toys by simply removing the magnets from the shaft.
In any of its 3 iterations the Moondrop makes for a satisfying fidget toy--flip it, slide it, spin it, or team up multiple pieces for a total workday distraction.